Positioning device for a radiation shield having means for cooling said shield



sMTROg XF? 3 395 igm V. L. MOORE POSITIONING DEVICE FOR A RADIATION SHIELD HAVING MEANS FOR COOLING SAID SHIELD Filed Nov. 30, 1964 July 30, 1968 PARTICLE SOURCE C 3i I I FIG. .3 g

24 27 INVENTOR \(FHHIL x 23 .2 I VLMOORE k Q m ATTORNEYS United States Patent 3,395,279 POSITIONING DEVICE FOR A RADIATION SHIELD HAVING MEANS FOR COOLING SAID SHIELD Vernon L. Moore, Bartlesville, Okla., assignor to Phiilips Petroleum Company, a corporation of Delaware Filed Nov. 30, 1964, Ser. No. 414,821 1 Claim. (Cl. 250105) ABSTRACT OF THE DISCLOSURE This invention relates to apparatus for selectively positioning an element in different locations.

Charged particle accelerators are being used quite ex- ,tensively for analysis and research purposes. In many applications it is desirable to be able to block the particle Beam from the target area without shutting down the accelerator. This is often accomplished by selectively positioning a metal shield in the particle beam. Shields employed for this purpose are commonly referred to as Faraday cups. The selective movement of such a shield into and out of the particle beam is complicated by the fact that the apparatus is operated at a low pressure, such as mm. of Hg, for example. One procedure for moving shields which has been employed heretofore involves mounting the shield on the end of a metal bellows. The shield can thus be moved into the particle beam by expanding the bellows. However, these bellows have-been found to have relatively short lives under normal operating conditions. The replacement of such a bellows is an expensive procedure and results in the accelerator being shut down while repairs are made.

In accordance with one specific embodiment of this invention, an improved device is provided for selectively positioning a metal shield in a particle beam. A housing is secured to the wall of the accelerator tube. The housing is provided with a sleeve which carries a rotatable plug. An offset arm extends from the plug into the tube to support a shield at positions adjacent to or in the particle beam. By selectively rotating the plug, the shield can be moved into or out of the particle beam. The oifset arm is advantageously formed by a cooling tube so as to carry away heat generated by the beam impinging on the shield. The apparatus of this invention is constructed so that the shield can be insulated electrically from the accelerator housing.

Accordingly, it is an object of this invention to provide apparatus for selectively positioning an element in a radiation beam.

Another object is to provide an improved shield assembly for use with charged particle accelerators.

A further object is to provide an improved positioning device.

Other objects, advantages and features of the invention should become apparent from the following detailed description, taken in conjunction with the accompanying drawing in which:

FIGURE 1 is a view, shown partially in section, of a charged particle accelerator having the shield of this invention incorporated therein.

FIGURE 2 is a view, shown partially in section, of the shield of thi invention in a first position in the particle beam.

FIGURE 3 is a view, shown partially in section, of the shield displaced from the particle beam.

Referring now to the drawing in detail and to FIG- URE l in particular, there is shown a source 19 which is adapted to produce charged particles. Such a source can be a positive ion generator, for example. The resulting charged particles are directed through an accelerating tube 11 which is provided with a number of spaced electrodes 12. Suitable accelerating potentials are applied to the electrodes so that the charged particles produced in source 10 are accelerated through tube 11. The shielding assembly 13 of this invention is secured to the accelerating tube upstream from the target area. Conduits 14: and 15 communicate with the accelerating tube downstream from the shield. In some operations, charged particles are permitted to flow through tube 15 to strike a target external of the apparatus illustrated. In another method of operation, material to be irradiated can also be introduced into the system through tube 14, for example. A housing 16 contains a suitable vacuum pump, not shown, which is connected to the accelerating tube through conduit means 17 to evacuate the tube.

The shielding device of this invention is illustrated in FIGURES 2 and 3. The shield itself is formed of a metal cup 20. The supporting assembly for shield 20 is attached to a flange 21 which covers an opening in the wall of accelerating tube 11. Flange 21 can be so secured by means of screws 22, for example. A housing 23 is secured to and extends from flange 21. Housing 23 can be secured to the flange by welding or brazing, or the housing can be formed integral with the flange. A sleeve 24 is positioned within housing 23 and is secured thereto by a set screw 25 which prevents the sleeve from rotating relative to the housing. A rotatable plug 26 is positioned within sleeve 24 and is held in place by a retaining plate 27, the latter being secured to housing 23 by screws 28.

Plug 26 is provided with two spaced passages 29 and 30 which extend therethrough. A hollow tube 31 connects the inner ends of passages 29 and 30 and supports cup 20 As illustrated, tube 31 is offset from the axis of plug 26 so that cup 20 is displaced away from the particle beam in the center of tube 11 when the plug occupies the position illustrated in FIGURE 3. When plug 26 is rotated to the position illustrated in FIGURE 2, cup 20 is moved into the particle beam. Suitable flexible conduits, not shown, are connected to the outer end of plug 26 so that a coolant can be circulated through tube 31, This coolant carries heat away from cup 21 to prevent overheating when the cup is rotated into the particle beam.

Theapparatus of FIGURE 2 is provided with a number of sealing gaskets to prevent leakage of air into the Y evacuated accelerating tube. Two spaced O-rings 33 and 34 are carried by housing 23 so as. to engage sleeve 24. An O-ring 35 is carried by flange 21 so as to engage sleeve 24. O-rings 36, 37 and 38 are carried by plug 26 so as to engage the inner surface of sleeve 24.

As previously mentioned, it is desirable that cup 20 be insulated electrically from the accelerating tube. This is accomplished by constructing sleeve 24 and retaining plate 27 of insulating material. Ceramic filled Teflon, for example, can be employed to advantage for the construction of bearing sleeve 24. Any suitable insulating material can be employed in the construction of retaining plate 27.

While plug 26 can be rotated manually, it is desirable to provide a motor drive so that movement of the shielding cup can be controlledfrom a location remote from the accelerator. This is accomplished by mounting a spur gear 40 on plug 26. Spur gear 40 is also formed of an insulating material to keep the cup insulated from the housing. A reversible motor 41, see FIGURE 1, is secured to housing 16 adjacent the shieldassembly. The drive shaft of motor 41 carries a worm 42 which engages gear 40 to rotate plug 26. The control circuit for the motor can thus be positioned remote from the accelerator to provide for selective rotation of the shield into and out of the particle beam.

While this invention has been described in conjunction with a presently preferred embodiment, it should be evident that it is not limited thereto. For example, the positioning device can be employed to move a target material selectively into a radiation beam.

What is claimed is:

1. In a radiation device comprising in combination a metal housing, a radiation source projecting a beam of radiation into said housing, a metal plug extending through said housing and mounted therein in rotatable gas-tight relationship, and a metal shield on said plug ofiset from its axis of rotation adapted to be rotated into a first position interrupting said beam and a second position allowing passage of said beam, the improvement com prising mounting said plug for rotation with a sleeve of electric insulating material disposed between said plug 20 and said housing whereby electrical energy received by said shield is insulated from said housing, and providing sealing means between the relatively rotatable metal plug and the sleeve of electric insulating material to prevent any appreciable passage of gas therebetween, said shield being provided with an indirect heat exchange cooling means comprising a first conduit extending through said plug and means to circulate cooling fluid through said first conduit comprising a second flexibleisupply conduit connected to said first conduit.

References Cited UNITED STATES PATENTS 2,566,037 8/1951 Shewell 250-41.9 2,851,610 9/1958 Akashi et al. 250-495 2,877,353 3/1959 Newberry 25049.5 3,072,786 1/1963 Jones et al. 25049.5 3,102,194 8/1963 Van denBroek etal. 25049.5 3,165,658 1/1965 Zunick.

FOREIGN. PATENTS 954,900 12/ 1956 Germany.

RALPH G. NILSON, Primary Examiner. A. L. BIRCH, Assistant Examiner. 

